They are both forms of agate. The value of most agate is not all that high. Sometimes pieces from certain places or rare colors command higher prices. There are many, many varieties and colors of agate.
The first pic is a slab from an agate nodule or geode, maybe .50-$1.00
Second pic is slab from what appears to be a stalactite/mite, as noted by EDDE. It is beautiful! A very nice slab! Value? Don't really know! Could be anywhere from $5.00- $15.00+